To allow the support and height-adjustable mounting of headrests, welded pieces of pipe or openings are customarily mounted in the upper regions of backrests, and are in turn used to affix guide sleeves for height-adjustably receiving the headrest rods of the headrest frame.
The guide sleeves must maintain the adjusted height position of the headrest, must also absorb torque and axial forces in the event of a crash; in addition, auxiliary components, such as controls that will allow removal of the headrest or adjustment of its position, must be accommodated to some extent. In this connection, the adjustment functions should glide easily, and the mounting forces should be low; furthermore, all of the adjustable positions for the headrest should be implemented without rattling during driving.
In practice, these requirements are frequently difficult or impossible to fulfill. To allow low adjustment forces, guide sleeves are frequently configured with a degree of play relative to the headrest rods, or high adjustment forces are established and grease is used to some extent on the guide rods.
For the components, strict requirements with regard to dimensional consistency and precision of positioning result, which in turn leads to high manufacturing and assembly costs. In particular, headrest frames having a very precise degree of parallelism and a precise track width result in high manufacturing costs.
One mounting device of the above-mentioned type is known from WO 2004/062963 A1. The headrest frame is height-adjustably received by its two headrest rods (or legs) in a first and a second guide sleeve. The first guide sleeve is secured and held within the receptacle device, which is secured in the backrest, and for which purpose, for example, a catch on the guide sleeve can latch into the receptacle device that is secured in the backrest. The second guide sleeve is held inside a support that widens into a funnel shape toward the top and toward the bottom from an upper pivot point, for the purpose of compensating for tolerances, with the support being pivotably held within a second receptacle device secured in the backrest.
Tolerances or dimensional variations in the headrest rods and the receptacle devices secured in the backrest are thus compensated for by the second receptacle device, to which end the support is able to pivot around a ball-joint-type connection on the second guide sleeve. A mounting device of this type makes it possible to compensate for even sizable dimensional variations, thus allowing the use of more cost-effective headrest frames, without requiring an excessive amount of force be applied to the headrest rods in order to adjust the height of the headrest. The friction between the guide sleeves and the headrest rods remains substantially constant. A latching mechanism is provided for the respective height adjustment is provided between the securely mounted guide sleeve and its headrest rod.
However, a mounting device of this type involves a complex construction with multiple components, and a correspondingly high assembly cost.